A hydrogen recirculating-type fuel cell system is known in the art, which is provided with a fuel cell stack generating electric power by an electrochemical reaction of hydrogen gas and oxygen, a hydrogen gas feed path connecting an inlet of a hydrogen gas passage formed inside the fuel cell stack and a hydrogen gas source with each other, a hydrogen gas feed valve arranged inside the hydrogen gas feed path, an anode off-gas passage connected to an outlet of the hydrogen gas passage, a hydrogen gas return passage connecting the anode off-gas passage and the hydrogen gas feed path upstream of the hydrogen gas feed valve with each other, and a hydrogen gas return pump arranged inside the hydrogen gas return passage. In this hydrogen recirculating-type fuel cell system, unused hydrogen gas flowing out from the fuel cell stack is returned by the hydrogen gas return pump to the hydrogen gas feed path, therefore the hydrogen gas is effectively utilized.
In this regard, in a hydrogen recirculating-type fuel cell system, a hydrogen gas return passage and a hydrogen gas return pump are necessary, so the configuration becomes complicated and the cost increases. Not only this, space is required for installing the hydrogen gas return passage and hydrogen gas return pump. Therefore, a non-hydrogen recirculating-type fuel cell system is known in the art, in which a purge passage is connected to an outlet of the hydrogen gas passage of the fuel cell stack and is separated from the hydrogen gas feed path, and a purge control valve is arranged inside the purge passage (see PLT 1). In this non-hydrogen recirculating-type fuel cell system, the hydrogen gas return passage and hydrogen gas return pump are eliminated. Therefore, unused hydrogen gas flowing out from the fuel cell stack is not returned to the hydrogen gas feed path.